In-between Boundaries

While the highway infrastructure of North America provides great benefits by connecting both urban and rural communities, this infrastructure also comes with significant costs by separating and creating barriers between various communities. The Sunnyside beach area in Toronto is an example of an important public area isolated by the Gardiner Expressway from the neighborhoods of Swansea, Sunnyside, Roncesvalles Village, and Parkdale. This thesis explores two prototype strategies for urban and architectural interventions on two sites in the Sunnyside area by both bridging over the Gardiner Expressway and traversing underneath it, as an approach that could be applied in other key locations along arterial urban highways. Implementation of these reconnection strategies would provide an opportunity to add significant new activity programs in the Sunnyside area. The programming and spatial character of former recreation activities and facilities at Sunnyside are used within a process of urban memory retrieval to organise the proposed new buildings. Within the buildings, interior boundaries - walls between rooms - are eliminated as static space dividers and replaced as expanded functional space. In-between Boundaries offers a systematic perspective for analysing a range of design scales for the built environment from urban design to site and building design scales and, in so doing, proposes an enhanced degree of complexity and continuity in architectural design

Gradient estimates for porous medium and fast diffusion equations by martingale method

International audienceIn this paper, we establish several local and global gradient estimates for the positive solution of Porous Medium Equations (PMEs) and Fast Diffusion Equations (FDEs). Our proof is probabilistic and uses martingale techniques

Bioactive polydimethylsiloxane surface for optimal human mesenchymal stem cell sheet culture

Human mesenchymal stem cell (hMSC) sheets hold great potential in engineering three-dimensional (3D) completely biological tissues for diverse applications. Conventional cell sheet culturing methods employing thermoresponsive surfaces are cost ineffective, and rely heavily on available facilities. In this study, a cost-effective method of layer-by-layer grafting was utilized for covalently binding a homogenous collagen I layer on a commonly used polydimethylsiloxane (PDMS) substrate surface in order to improve its cell adhesion as well as the uniformity of the resulting hMSC cell sheet. Results showed that a homogenous collagen I layer was obtained via this grafting method, which improved hMSC adhesion and attachment through reliable collagen I binding sites. By utilizing this low-cost method, a uniform hMSC sheet was generated. This technology potentially allows for mass production of hMSC sheets to fulfill the demand of thick hMSC constructs for tissue engineering and biomanufacturing applications

Effects of short term hypoxia-preconditioning on glial phenotype induction of human mesenchymal stem cells

Development of successful clinical treatments for peripheral nerve injury is limited due to the complications behind neural physiology. Human mesenchymal stem cells (hMSCs) have the ability to directly promote tissue repair and protect cells at the injury site. Studies have shown that hMSCs can be transplanted to improve nerve regeneration. Hypoxic culture condition has been proven to maintain the stemness of hMSCs for later differentiation. In this study, we investigated the effects of low oxygen (O2) (2% and 5% O2) pre-treatment and initial seeding density (500, 1000, and 2000 cells/cm2) on glial protein expression during glial differentiation of hMSCs. Results showed that the secretion of glial proteins was tunable by modifying the seeding density. Moreover, glial induction of hMSCs, characterized by the glial fibrillary acidic protein (GFAP) and S100β expressing phenotype, were enhanced by short-term hypoxia pretreatment. The significantly increased gene expression, including GFAP (10 folds in 2% O2, 25 folds in 5% O2), 2’,3’-Cyclic Nucleotide 3’ Phosphodiesterase (CNP) (600 folds in 2% O2, 800 folds in 5% O2), and neural growth factor receptor (NGFR) (4 folds in 5% O2), indicated that low oxygen, especially 5% O2 pretreated hMSCs had an improved potential for peripheral nerve regeneration

Engineering stem cell cardiac patch with microvascular features representative of native myocardium

The natural myocardium is a highly aligned tissue with an oriented vasculature. Its characteristic cellular as well as nanoscale extracellular matrix (ECM) organization along with an oriented vascular network ensures appropriate blood supply and functional performance. Although significant efforts have been made to develop anisotropic cardiac structure, currently neither an ideal biomaterial nor an effective vascularization strategy to engineer oriented and high-density capillary-like microvessels has been achieved for clinical cardiovascular therapies. A naturally derived oriented ECM nanofibrous scaffold mimics the physiological structure and components of tissue ECM and guides neovascular network formation. The objective of this study was to create an oriented and dense microvessel network with physiological myocardial microvascular features. Methods: Highly aligned decellularized human dermal fibroblast sheets were used as ECM scaffold to regulate physiological alignment of microvascular networks by co-culturing human mesenchymal stem cells (hMSCs) and endothelial cells (ECs). The influence of topographical features on hMSC and EC interaction was investigated to understand underlying mechanisms of neovasculature formation. Results: Results demonstrate that the ECM topography can be translated to ECs via CD166 tracks and significantly improved hMSC-EC crosstalk and vascular network formation. The aligned ECM nanofibers enhanced structure, length, and density of microvascular networks compared to randomly organized nanofibrous ECM. Moreover, hMSC-EC co-culture promoted secretion of pro-angiogenic growth factors and matrix remodeling via metalloprotease-2 (MMP-2) activation, which resulted in highly dense vascular network formation with intercapillary distance (20 μm) similar to the native myocardium. Conclusion: HMSC-EC co-culture on the highly aligned ECM generates physiologically oriented and dense microvascular network, which holds great potential for cardiac tissue engineering

Open X-Embodiment:Robotic learning datasets and RT-X models

Large, high-capacity models trained on diverse datasets have shown remarkable successes on efficiently tackling downstream applications. In domains from NLP to Computer Vision, this has led to a consolidation of pretrained models, with general pretrained backbones serving as a starting point for many applications. Can such a consolidation happen in robotics? Conventionally, robotic learning methods train a separate model for every application, every robot, and even every environment. Can we instead train "generalist" X-robot policy that can be adapted efficiently to new robots, tasks, and environments? In this paper, we provide datasets in standardized data formats and models to make it possible to explore this possibility in the context of robotic manipulation, alongside experimental results that provide an example of effective X-robot policies. We assemble a dataset from 22 different robots collected through a collaboration between 21 institutions, demonstrating 527 skills (160266 tasks). We show that a high-capacity model trained on this data, which we call RT-X, exhibits positive transfer and improves the capabilities of multiple robots by leveraging experience from other platforms. The project website is robotics-transformer-x.github.io

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

FABRICATION OF PREVASCULARIZED CELL-DERIVED EXTRACELLULAR MATRIX BASED BIOMIMETIC TISSUE CONSTRUCTS FOR MULTIPLE TISSUE ENGINEERING

Tissue engineering and regenerative medicine has been vast developing since the past decade. A preformed functional vascular network provides effective solution for solving the mass transportation problem. With the support of mural cells, endothelial cells (ECs) can form microvessels within engineered tissues. As one of the important mural cells, human mesenchymal stem cells (hMSCs) not only stabilize the engineered microvessel network, but also preserve their multi-potency when grown under optimal culture conditions. A prevascularized hMSC/ECM sheet fabricated by the combination of hMSCs, ECs and a naturally derived nanofibrous extracellular matrix (ECM) scaffold offers great opportunity for engineering mechanically strong and completely biological 3D prevascularized tissues. Moreover, for regeneration of highly organized tissues such as skeletal, cardiac, and neural tissues, it is critical to create aligned vasculatures within the constructs, which not only provide inlets/outlets for ease of vessel anastomosis, but also play important roles in tissue functional performance. The topographical stimulation enhanced the structure, density, and length of the vascular networks by promoting pro-angiogenic growth factor secretion and guiding neovasculature orientation. The matrix remodeling enzymatic activity assessment revealed that CD166 mediated MMP-2 activation played a major role in angiogenesis and vasculature remodeling direction. Preliminary studies have shown that hMSCs can be transplanted to improve nerve regeneration. Hypoxia pretreated hMSCs had an improved potential for peripheral nerve regeneration. The future works can focus on studying the neural protective functions of MSCs, and how prevascularized scaffolds can restore the oxygen supply towards the hypoxic region upon ischemia or injury. In summary, prevascularized nanofibrous ECM constructs can serve as building blocks to engineer 3D oriented tissues with aligned vasculatures, while preserving the therapeutic potential of bulk hMSCs. Together, this study paved the way for engineering large organs, and provided a perspective on replicate native cell/ECM/vessel structure to benefit regenerative medicine